1. Field of the Invention
The present invention relates to an anti-toppling device for a construction machine capable of preventing completely the toppling of a construction machine which moves by means of a mobile platform and performs operations by means of a plurality of operating tools.
2. Description of the Related Art
Conventionally, anti-toppling devices for construction machinery have been most advanced in the field of cranes, and anti-toppling algorithms used therein have essentially been implemented as follows.
(1) the total load moment about the boom fulcrum is calculated from the axial force in the hydraulic cylinder of the boom and the angle of the boom; PA1 (2) the moment about the boom fulcrum due to the operating tools alone is calculated from the angles of all the operating tools and the weight and centre of gravity of all the operating tools; PA1 (3) the magnitude of suspended loads is found from (1) and (2) above by dividing by the distance to the position of each suspended load; PA1 (4) the toppling moment generated by the operating tools about the toppling fulcrum is found from the weight, centre of gravity, suspended load and position of suspended load for each operating tool; and PA1 (5) a value derived by multiplying a safety coefficient to the stability moment generated about the toppling fulcrum by the weight of the vehicle excluding the operating tools is recorded. Judging means for judging if the toppling moment in (4) above exceeds this value are provided, and an anti-toppling measures are taken by issuing an alarm, and halting the operating tools, etc., on the basis of the results from the judging means.
Furthermore, an anti-toppling device of this kind has also been applied to a construction machine such as a hydraulic shovel, or the like (Japanese Patent Publication 2-45737, Japanese Laid-open Patent Application 5-202535).
Incidentally, in construction machines such as the crane or hydraulic shovel described above, only a single operating tool is mounted on the mobile platform, and therefore the anti-toppling device performs anti-toppling calculations with respect to one operating tool only.
However, in construction machines having a plurality of operating tools on a single mobile platform, each operating tool is capable of turning independently, and in some cases, operating tools are used conjointly in the same direction, so when an operating tool is holding a load in this direction, there is the risk that the construction machine will topple over, whereas if the operating tools are positioned in opposing directions, the device will not be liable to topple over, even if it is holding a load or loads.
In a construction machine comprising a plurality of operating tools on a single mobile platform, the positional relationships between the different operating tools vary widely, including their direction of rotation, and the moments of the operating tools vary widely depending on their direction of rotation. Therefore, even if these moments are calculated simply on the axial drive force of the boom and the angle of operation, it is not simple to determine the possibility for the construction machine as a whole to topple over.
Furthermore, it is also difficult for a person operating a construction machine generating complex moments of this kind to determine instantly how he or she should operate the operating tools in order to avoid toppling, and a suitable device for avoiding toppling is difficult to design.